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1、ObjectMapper与JSONObject比较

1、ObjectMapper属于jackson库的一部分,JSONObject属于alibaba的fastjson，两者各有优劣，可根据自己的系统环境选择使用哪种技术。

2、目前来看，Jackson社区相对活跃，Spring MVC和Spring Boot都默认使用Jackson。

核心主要有三个部分：

jackson-core(核心包)、jackson-databind(数据绑定包)、jackson-annotations(注解包)

3、依赖包不同

//JSONObject依赖包<dependency><groupId>com.alibaba.fastjson2</groupId><artifactId>fastjson2</artifactId><version>2.0.42</version></dependency>//ObjectMapper依赖包<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.14.2</version></dependency>

2、ObjectMapper使用概述

ObjectMapper通过writeValue()实现序列化，通过readValue()实现反序列化。

ObjectMapper通过Feature枚举类，初始化了很多的默认配置。

2.1、工程的pom.xml导包信息

spring-boot-starter-web包中包含了jackson包，不需要单独导入

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.7.17</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.txc</groupId><artifactId>objectmapper</artifactId><version>0.0.1-SNAPSHOT</version><name>objectmapper</name><description>objectmapper</description><properties><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><configuration><excludes><exclude><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></exclude></excludes></configuration></plugin></plugins></build></project>

2.2、创建案例中的测试对象

案例中使用lombok注解生成get和set方法，也可以直接写get和set方法

@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class Student {private String stu_id;private String stu_name;
}

2.3、对象和JSON相互转化

2.3.1、测试代码

/*** 实现对象和JSON之间互转*/
@RequestMapping("/jsonObjectChange")
@ResponseBody
public  void  jsonObjectChange() throws Exception{ObjectMapper mapper = new ObjectMapper();String param = "{\"stu_id\":\"1001\",\"stu_name\":\"晓春\",\"stu_sex\":\"男\",\"stu_age\":\"34\",\"stu_addr\":\"安徽合肥\",\"stu_pwd\":\"123456\"}";//将字符串转换为对象—反序列化过程Student student = mapper.readValue(param, Student.class);System.out.println("===json转对象==="+student.toString());//将对象转化成JSON—序列化过程String  json = mapper.writeValueAsString(student);System.out.println("===对象转json==="+json);
}

2.3.2、测试结果展示

2.4、集合和JSON像话转化

2.4.1、测试代码

/*** 集合和JSON相互转化*/
@RequestMapping("/listAndJSONChange")
@ResponseBody
public void  arrayToObject() throws Exception{Student student1=new Student("1001","晓春1","男","34","安徽合肥","123456");Student student2=new Student("1002","晓春2","男","34","安徽合肥","123456");ObjectMapper mapper = new ObjectMapper();//集合转jsonString param = mapper.writeValueAsString(Arrays.asList(student1,student2));System.out.println("==集合转json=="+param);//数组json转化成集合List<Student> list= mapper.readValue(param, List.class);System.out.println("==数组json转集合=="+list);
}

2.4.2、测试结果展示

2.5、Map和JSON相互转化

2.5.1、测试代码

/*** map和json相互转化*/
@RequestMapping("/mapAndJsonChange")
@ResponseBody
public void  mapAndJsonChange() throws Exception{ObjectMapper mapper = new ObjectMapper();Map<String, Object> map = new HashMap<>();map.put("id", "1001");map.put("name","晓春");map.put("student", new Student("6","6","6","6","6","6"));String param = mapper.writeValueAsString(map);System.out.println("===map转json==="+param);Map<String, Object> resultMap = mapper.readValue(param, Map.class);System.out.println("===json转map==="+resultMap);
}

2.5.2、测试结果展示

3、常见的ObjectMapper配置及问题总结

3.1、如果生成的JSON使用的是单引号，解析会失败

问题的json样式：String param="{'stu_id':'1001','stu_name':'晓春'}";

默认支持的是双引号，在很多的环境中都是。

解决博客地址：https://blog.csdn.net/tangshiyilang/article/details/134275584

3.2、生成的JSON字符串属性没有双引号或者单引号问题

问题json样式：String param="{stu_id:\"1001\",stu_name:\"晓春\"}";

解决博客地址：

4、源码下载

源码需要积分

https://download.csdn.net/download/tangshiyilang/88512083